feat: add support for building iOS wheels. (#2286)

* Add support for building iOS wheels.

* Replace use of system() in test binary module.

* Restored the 'minimal' approach of the minimal examples.

* Split out platform details into standalone pages, and expand iOS platform details.

* More doc corrections.

* Bump support package to include fix for python/cpython#130292

* Ensure iOS tests are all run on the same xdist worker.

* More iOS documentation tweaks.

* Factor out common xcode version test utility.

* Simplify iOS to a single platform with an expanded interpretation of arch.

* I guess I should update the iOS tests as well...

* Additional safety for missing iOS test output.

* Remove DYLD_LIBRARY_PATH from the iOS environment.

* Make test-sources mandatory for iOS builds.

* Updates and clarifications to documentation.

* Clarify what a slice is.

* Normalize use of underscores in platform name.

* Modify auto target to be matching CPU only.

* Use consistent ordering of platforms in examples.

* Use consistent naming in iOS archiectures.

* Placate the linter.

* Miscellaneous cleanups picked up by @joerick's review.

* Correct the list of expected wheels.

* Correct which 'native' we're actually checking.

* Correct the docs links so they're all relative.

* Correct the identification of free threaded builds.

* Use target instead of host to describe the platform we're building for.

* Rework iOS test to remove issue with log completeness.

* Convert errors to FatalError

Co-authored-by: Matthieu Darbois <mayeut@users.noreply.github.com>
Co-authored-by: Joe Rickerby <joerick@mac.com>

* Removed a repeated check for a valid python.

* Update bin/update_pythons.py to update iOS support packages.

* Document that iOS CI is available on other platforms.

* Restore a comment needed for some platforms.

* Small cleanups identified in code review

Co-authored-by: Joe Rickerby <joerick@mac.com>

* Simplify logic to appease linter.

* Modify dependency constraint handling to use new API.

* Cosmetic change to trigger a CI rebuild.

---------

Co-authored-by: Matthieu Darbois <mayeut@users.noreply.github.com>
Co-authored-by: Joe Rickerby <joerick@mac.com>

cibuildwheel/architecture.py

@@ -17,6 +17,7 @@ PRETTY_NAMES: Final[dict[PlatformName, str]] = {
     "macos": "macOS",
     "windows": "Windows",
     "pyodide": "Pyodide",
+    "ios": "iOS",
 }
 
 ARCH_SYNONYMS: Final[list[dict[PlatformName, str | None]]] = [
@@ -63,6 +64,12 @@ class Architecture(StrEnum):
     # WebAssembly
     wasm32 = auto()
 
+    # iOS "multiarch" architectures that include both
+    # the CPU architecture and the ABI.
+    arm64_iphoneos = auto()
+    arm64_iphonesimulator = auto()
+    x86_64_iphonesimulator = auto()
+
     @staticmethod
     def parse_config(config: str, platform: PlatformName) -> "set[Architecture]":
         result = set()
@@ -89,8 +96,8 @@ class Architecture(StrEnum):
 
     @staticmethod
     def native_arch(platform: PlatformName) -> "Architecture | None":
-        if platform == "pyodide":
-            return Architecture.wasm32
+        native_machine = platform_module.machine()
+        native_architecture = Architecture(native_machine)
 
         # Cross-platform support. Used for --print-build-identifiers or docker builds.
         host_platform: PlatformName = (
@@ -99,8 +106,18 @@ class Architecture(StrEnum):
             else ("macos" if sys.platform.startswith("darwin") else "linux")
         )
 
-        native_machine = platform_module.machine()
-        native_architecture = Architecture(native_machine)
+        if platform == "pyodide":
+            return Architecture.wasm32
+        elif platform == "ios":
+            # Can only build for iOS on macOS. The "native" architecture is the
+            # simulator for the macOS native platform.
+            if host_platform == "macos":
+                if native_architecture == Architecture.x86_64:
+                    return Architecture.x86_64_iphonesimulator
+                else:
+                    return Architecture.arm64_iphonesimulator
+            else:
+                return None
 
         # we might need to rename the native arch to the machine we're running
         # on, as the same arch can have different names on different platforms
@@ -131,9 +148,13 @@ class Architecture(StrEnum):
             elif Architecture.aarch64 in result and _check_aarch32_el0():
                 result.add(Architecture.armv7l)
 
-        if platform == "windows" and Architecture.AMD64 in result:
+        elif platform == "windows" and Architecture.AMD64 in result:
             result.add(Architecture.x86)
 
+        elif platform == "ios" and native_arch == Architecture.arm64_iphonesimulator:
+            # Also build the device wheel if we're on ARM64.
+            result.add(Architecture.arm64_iphoneos)
+
         return result
 
     @staticmethod
@@ -150,6 +171,11 @@ class Architecture(StrEnum):
             "macos": {Architecture.x86_64, Architecture.arm64, Architecture.universal2},
             "windows": {Architecture.x86, Architecture.AMD64, Architecture.ARM64},
             "pyodide": {Architecture.wasm32},
+            "ios": {
+                Architecture.x86_64_iphonesimulator,
+                Architecture.arm64_iphonesimulator,
+                Architecture.arm64_iphoneos,
+            },
         }
         return all_archs_map[platform]